Lipases are widely used in esterification reactions of various carboxylic acids such as a fatty acid with alcohols such as monoalcohol and polyalcohol or ester exchange reactions between several carboxylic esters. Among them, the ester exchange reactions are important technology including modification of fats and oils of animals and plants and as a method for producing esters of various fatty acids, sugar esters and steroids. When lipases that are fat and oil hydrolases are used as a catalyst in those reactions, ester exchange reactions can be conducted under the temperate condition of room temperature to about 70° C. Therefore, use of lipases can not only inhibit side reactions and reduce energy costs as compared with the prior chemical reactions, but also its safety is high because the lipases as the catalyst are natural products. Further, objective compounds can be effectively produced due to its substrate specificity or positional specificity. However, the lipase activity does not sufficiently develop when lipase powder is directly used in ester exchange reactions. In addition to it, it is difficult to equally disperse basically water-soluble lipases in oil-based raw materials and then to collect them. Therefore, conventionally, it is common that lipases are immobilized to some carriers such as anion-exchange resins (Patent Literature 1), phenol adsorption resins (Patent Literature 2), hydrophobic carriers (Patent Literature 3), cation-exchange resins (Patent Literature 4), and chelate resins (Patent Literature 5), and then used in esterifications and ester exchange reactions.
However, since the lipase activity lowers when immobilizing lipases to carriers, various technologies using lipase powder have been developed.
More concretely, the method has been suggested which comprises the steps of dispersing lipase powder in the raw material containing an ester(s) in the presence or absence of an inactive organic solvent(s); and then conducting the ester exchange reaction so that 90% or more of the dispersed lipase powder particles maintain the particle diameter of 1 to 100 μm in the ester exchange reaction (Patent Literature 6). Further, the method has been suggested to use enzymatic powder obtained by drying an enzymatic solution containing a phospholipid(s) and a lipophilic vitamin(s) (Patent Literature 7).
[Patent Literature 1] Japanese Patent Unexamined Publication No. Sho 60-98984
[Patent Literature 2] Japanese Patent Unexamined Publication No. Sho 61-202688
[Patent Literature 3] Japanese Patent Unexamined Publication No. Hei 2-138986
[Patent Literature 4] Japanese Patent Unexamined Publication No. Hei 3-61485
[Patent Literature 5] Japanese Patent Unexamined Publication No. Hei 1-262795
[Patent Literature 6] Japanese Patent No. 2668187
[Patent Literature 7] Japanese Patent Unexamined Publication No. 2000-106873